1. Field of the Invention
The invention generally relates to a Universal Serial Bus (USB) technique, and more particularly, to a USB apparatus having dual-function of a host and a hub, and a control method thereof.
2. Description of the Prior Arts
During the recent years, Universal Serial Bus (USB) is accounted as one of the most extensively applied standards in communication interfaces for information products. Nowadays, various peripheral devices can be connected to a computer host using USB interface such that prior complications of having to connect various peripheral devices using different connectors to a computer host can be solved. Furthermore, USB peripheral devices are developed with plug-and-play capabilities; that is, when installing or removing a USB peripheral device, it is unnecessary to shut down the computer host or install additional drivers.
According to USB specifications, a USB system comprises a USB host, a USB device and a USB inter-connection. The USB host is in charge of scheduling data transmission at the USB bus, and is generally embedded in a computer host. The USB device is classified into two categories: a hub for providing the USB bus with new USB ports, and a function device designating peripheral devices such as mice, keyboards, printers, thumb drives and so on. In a conventional USB system, the USB hub acts as a bridge interface between the USB function device and the USB host. In the absence of the USB host, even if the USB hub is connected with the USB function device, or the USB hub has an embedded USB function device, the USB function device is still considered as useless.